The present invention relates to compositions and methods of treating periodontal disease and related disorders utilizing a sustained, controlled release targeted delivery method to effectively disrupt and inhibit bacterial biofilms at periodontal treatment sites.
Periodontal diseases are a major affliction to mankind. Gingivitis, inflammation of gingival (gum) tissue, and periodontitis, inflammation and progressive loss of ligament and alveolar (socket) bone support to teeth, are caused by bacteria which colonize tooth surfaces and occupy the gingival crevice area. These are major periodontal disease afflictions worldwide. Bacterial plaque is the principal causative agent of these periodontal diseases.
Routine daily prevention or removal of plaque by the patient is a cornerstone of periodontal therapy. Toothbrushes, dental floss and various other oral hygiene instruments can be used. These devices require motor skill and dexterity. The daily routines for adequate plaque removal require the patient to be diligent, motivated, educated and skillful. Accordingly, such methods are effective only when used by motivated individuals and then often to a limited extent.
Optimal response of the immune system to defend against bacterial assault is often not realized in patients prone to periodontal disease and the immune response may actually contribute to the disease process.
Conventional periodontal therapy has emphasized mechanical removal of soft and hard accretions of bacteria (i.e., plaque and calculus) from the root surface via use of dental instruments placed into the gingival crevice to mechanically shear the accretions from the tooth structure. See S. Kakehashi and P. F. Parakkal, Proceedings from the State of Art Workshop on Surgical Therapy for Periodontitis, J. Periodontal 53:475 (1982). However, scaling and root planning is often only partially effective in the removal of these accretions. Moreover, the removal is transient and the bacteria re-colonize the root surface.
Adjunctive therapies have been suggested for the treatment of periodontal diseases. Systemic antibiotics have been used in the periodontal therapy. See R. J. Genco, Antibiotics in the Treatment of Human Periodontal Diseases, J. Periodontal 52:545 (1981). However, systemic delivery (e.g., oral or intramuscular) typically does not provide a sufficient concentration of antibiotic over an extended period of time to the gingival crevice area.
Applicant""s U.S. Pat. No. 4,685,883 deals with controlled sustained release of chemotherapeutic agents in a bioerodable matrix in the periodontal pocket lesion via placement of the matrix in the periodontal pocket lesion with dental instruments. In one embodiment, the chemotherapeutic agents are incorporated into microspheres. These agents, although in sufficient concentration in the gingival crevice or periodontal pocket lesion, may not be able to adequately penetrate into the mass of the residual bacterial accretions on the tooth surfaces. Moreover, the bacterial accretions can rapidly reform.
Although specific bacteria are essential agents for many periodontal disease, their presence alone on the tooth surface and underneath the gingiva is not sufficient to explain the periodontal disease process. Rather, the host must react to this bacterial challenge if disease is to develop and progress. As with other bacterial infections, the host""s immune system acts locally at the invasion site and attempts rapidly to neutralize, remove, or destroy the bacterial agents. In periodontal disease, however, chronic bacterial plaque accumulation causes an excessive and persistent antigenic stimulus. Therefore, the host response, rather than being protective and self-limiting, can be destructive. See R. C. Page, Periodontal Disease, p. 221, Lea and Febiger, Philadelphia, 1989.
Applicant""s U.S. Pat. No. 5,939,047 deals with a controlled release topical delivery system to facilitate absorption and deposition of host immune system modulating agents into the gingival and oral mucosal tissues adjacent to the periodontium to dampen deleterious effects of host cell immune response to the periodontal bacteria challenge. If the bacterial challenge remains persistent, however, the host immune response can remain excessive and persistent.
Recent attention has been given to removing unwanted biofilms forming in various industrial processes. Biofilms are notoriously resistant to removal. The tendency of bacteria to adhere, secrete an adhesive extra cellular matrix and grow is a strong evolutionary advantage difficult to overcome. See J. W. Costerson, et al, Microbial biofilms, Annu Rev Microbiol 49:711 (1995). So far, little success has been realized. In early stages a biofilm is comprised of a cell layer attached to a surface. The cells grow and divide, forming a dense mat numerous layers thick. When sufficient numbers of bacteria are present (quorum) they signal each other to reorganize forming an array of pillars and irregular surface structures, all connected by convoluted channels that deliver food and remove waste. The biofilm produces a glycocalyx matrix shielding them from the environment. Urinary tract and urinary catheter infections are examples of biofilm infections.
As the biofilm matures, the bacteria become greatly more resistant to antibiotics than when in the planktonic (free cell) state. See H. Anwar, et al, Establishment of aging biofilms: a possible mechanism of bacterial resistance to antimicrobial therapy, Antimicrob Agents Chemother 36:1347 (1992). The host immune system is also significantly less effective against bacteria in the biofilm state. See E. T. Jensen, et al, Human polymorphonuclear leukocyte response to Pseudomonas aeruginosa biofilms, Infect Immun 5:2383 (1990). Certain bacterial strains may be able to confer resistance protecting the biofilm from host defense components that would otherwise bind to the surface of viable bacteria and kill them. See D. Grenier and M. Belanger, Protective effect of Porphyromonas gingivalis outer membrane vessicles against bactericidal activity of human serum, Infect Immun 59:3004 (1991). Yet the bacterial biofilm exudes lipopolysccharide agitating the host inflammatory response which, in periodontitis, contributes to the tissue destruction.
For Gram-negative bacteria, the signal components in quorum sensing are antoinducers, acylated homoserine lactones (AHLs). These highly membrane-permeable compounds diffuse out of and into the cells and accumulate in localized environments, as the growing population of bacteria increases. At a threshold concentration the antoinducers trigger gene transcription in the localized population of bacteria, activating biochemical pathways and physiological functions appropriate for growth and survival of the bacteria in that environment.
Agents which can inhibit AHLs would be beneficial in biofilm disruption or inhibition. Furanones are potential antagonists of AHLs. See S. Srinivasan, et al, Extracellular signal molecule(s) involved in the carbon starvation response of marine vibrio sp. strain S14, J. Bacteriol 180:201 (1998).
Synthetic histatin analogues have shown potential for reduction of viable bacterial counts in the oral biofilm model. dhvar 4 shows action against Gram-negative bacteria. A possible explanation for this finding is that dhvar 4 binds to the negatively charged lipopolysaccharide (LPS) moiety, which is specific for Gram-negative bacteria. Certain Gram-negative bacteria are involved in the development of periodontal disease. The involvement of LPS in the initial binding of amphipathic basis antimicrobial peptides to the bacterial membrane has been reported. Furthermore, comparison of the amino acid sequence of dhvar 4 with bactericidal/permeability-increasing protein (BPI) revealed that the N-terminal 5 amino acids of dhvar 4 show strong homology with the LPS binding domain of BPI. See E. J. Helmerhorst, et al, The effects of histatin-derived basic antimicrobial peptides on oral biofilms, J. Dent Res 78: 1245 (1999).
The present invention solves these and other problems by optimal delivery of biofilm disruption and inhibition agents at localized periodontal treatment sites.
The present invention relates to the use of time release biodegradable microshapes for sustained, controlled, targeted delivery of agents to disrupt and inhibit the formation of biofilms at localized periodontal treatment sites. The method involves the insertion of biodegradable microshapes containing agents active against bacterial biofilms into the gingival crevice or periodontal pocket region.
In one embodiment of the present invention, biodegradable, time-release microspheres containing agents generally disruptive of bacterial biofilms are delivered by a syringe or other dental instrument. In another embodiment of the present invention, microspheres containing agents generally inhibitive of bacterial biofilms are delivered similarly.
In yet another embodiment of the present invention, biodegradable, time-release microspheres containing agents disruptive to specific bacteria within the biofilm are delivered by a syringe or dental instrument. In another embodiment of the present invention, microspheres containing agents which inhibit colonization of specific bacteria within the biofilms are similarly delivered.
In still another embodiment of the present invention, agents having other methods of action (antibiotics, host modulation agents, etc.) are delivered in microspheres along with agents in microspheres effective against the biofilm by syringe or dental instrument. These agents have synergy in their effectiveness with this embodiment of the present invention.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages and objectives obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter in which there is illustrated and described preferred embodiments of the invention.